In an overlapped multiplexing system, namely, an OvXDM system, during conventional decoding, a node in a Trellis diagram needs to be continuously accessed. In addition, two memories are disposed for each node. One memory is configured to store a relatively best path for reaching the node, and the other memory is configured to store a measurement corresponding to the relatively best path for reaching the node.
Using an OvTDM system as an example, each node in a trellis diagram needs to be extended in a decoding process. Therefore, a quantity of nodes determines decoding complexity. For a system in which a total number of times of overlapping is K and whose modulation dimensionality is M (M is an integer and is greater than or equal to 2), a quantity of nodes that are in a stable state in a trellis diagram corresponding to the system is MK-1, and therefore decoding complexity increases exponentially with the total number K of times of overlapping. However, in the OvTDM system, spectral efficiency of the system is 2K/symbol, and therefore the spectral efficiency is higher if the total number K of times of overlapping is larger. Therefore, on one hand, because of a requirement for improving the spectral efficiency, it is better if the total number K of times of overlapping is larger; on the other hand, because of a requirement for reducing the decoding complexity, it is better if the total number K of times of overlapping is smaller. Particularly, when the total number K of times of overlapping increases to a specific value, for example, K is greater than 8, the decoding complexity increases sharply. An existing decoding method cannot meet a real-time decoding requirement, and a requirement for the spectral efficiency and a requirement for the decoding complexity and decoding efficiency are contradictory.